(b) I believe from the rumormill that a fast CryptoNight implementation from day 1 of XMR was worth something north of $400k in net profit. Just as a comparison against the value of keeping an optimized implementation private.
It is easy to throw out these crazy numbers in hindsight, knowing the coin was going to explode in value.
The coin traded for about 0.0002 or below for the first two weeks (total daily mining output <$3K). For the next week it traded at about 0.001 (total daily mining output about $14K).
At that point public optimized miners started getting released and having an obvious effect on the hash rate (so we know they were being used, and the 100% monopolization assumption becomes increasingly implausible), where it remained for the next few weeks while increasingly optimized public miners were released.
Profits from mining
and holding are speculation profits, not mining profits. People could make just as much by buying, and tens of thousands of coins were bought at those prices on OTC and cryptonote.exchange.to, so people were doing just that. Likewise, one could mine with an optimized miner at some huge advantage only to see the coin sink in value, but those too are speculation losses.
Nevertheless, I agree that a $1K bounty is uninteresting, and even $5K isn't that interesting unless you know for sure in advance that your approach is going to succeed (and that you will be the first one to get there). If you have to take risk, $5K is not nearly enough.